Carlos Queiroz has warned his Real Madrid side against complacency when they visit Monaco tonight.

The Spanish champions hold a 4-2 lead from the first leg but will be without England captain David Beckham in the Principality.

Beckham is suspended after a late booking against Monaco in the Bernabeu and has reportedly been given time off to spend with his family in Switzerland.

The former Manchester United star has been a huge hit following his move from Old Trafford last summer and has firmly established himself as one of Real's key players.

His absence will be keenly felt by the visitors but Queiroz insists his side still have enough quality to get through to a meeting with either Arsenal or Chelsea.

"We won the first half of the tie but that's not sufficient to qualify. Monaco are a good team with very good players," he said.

"We must have a positive attitude to get through this tie. Despite the two-goal advantage Real Madrid must play to its qualities and not with a defensive attitude.

"It's true that Beckham has his own style of play but we have confidence in our style of play. We have already experimented with playing without him. We must keep hold of the ball."

France midfielder Zinedine Zidane is also taking a cautious attitude towards the game.

He said: "I don't think qualification is achieved yet. This is a big game and we are not in the semi-finals yet. We played well in our last match [a 2-1 win at Albacete] and are in our best form for two or three weeks."

He stressed the importance of a good start, however.

"We must score first, if Monaco score first then it will be a different game. We will be playing against a good team in a strange atmosphere," added Zidane.

"We can't come here expecting to win, we must be at 100pc. If we go onto the pitch in the wrong frame of mind we could be in for a nasty surprise. This is the quarter-finals of the Champions League."

Roberto Carlos added: "We have a lead, but we are not going to settle for that and we will try and win the game. We never settle for a draw and we have to continue with that mentality because it has always worked out well for us."